Electrical musical instruments



J R. BRAND ET AL ELECTRICAL MUSICAL INSTRUMENTS Jan. 14, 1969 SheetFiled April 28, 1965 I INVENTOR. JOHN R. BRAND BY LEYJ: PLUNKETT CAI ONATTORNEY Jan. 14, 1969 Sheet 2 of 2 Filed April 28, 1965 JOHN R BRANDINVENTOR.

may J PL 11mm 2. 26 mm d. m: N BM R LT v a W- H.: J M 5N uw "0Q uw \VFLl 0Q m 1 A 2 N9. N W 3 W M 4l+ /& mm

United States 'Patent O 3,422,454 ELECTRICAL MUSICAL INSTRUMENTS John R.Brand, Northridge, and Bradley J. Plunkett, Van Nuys, Califl, assignorsto Warwick Electronics Inc., Chicago, III., a corporation of DelawareFiled Apr. 28, 1 965, Ser. No. 451,374 US. Cl. 841.0l Int. Cl. Gh 1/00;61% 3/00; G10]: 1/02 4 Claims ABSTRACT OF THE DISCLOSURE This inventionrelates to percussion circuits for a monophonic musical instrument, orthe monophonic portion of a polyphonic musical instrument. Specifically,the invention will be described with reference to a percussion circuitfor the pedal clavier of an electronic organ.

It is an object of this invention to provide a simplified andeconomicalpercussion circuit for the pedal clavier of an electronicorgan.

It is a further object of this invention to provide such a percussioncircuit which does not require any additional switches or contacts, butoperates from the actuation of the already existing padel clavierswitching.

In accordance with these and other objects which will become apparenthereinafter, preferred forms of the invention will be now described withreference to the accompany-ing drawings wherein:

FIGURE 1 is a circuit diagram of one form of the present invention, and

FIGURE 2 is a circuit diagram of a second form of the invention.

Referring to FIGURE 1, 11 designates a sequence of single pole,double-throw switches connected in monophoni'c sequence. That is, onlyone tone (a pedal tone) will be sounded by the organat any one time,irrespect ve of how many pedal keys may be depressed. when a pluralityof keys are depressed simultaneously, only the lowest pitch will sound.

Each double'throw switch of the switch sequence 11 consists of a pole12, a normally closed contact 13, and a normally-open contact 14. Eachpole 12 is'linked to a pedal key '15. which when actuated or played bythe. foot of the organist, moves the pole 12 from the normallyclosedcontact 13 to the normally-open contact 14. When the pedal key isreleased. the pole 12 is biased into contact with the'normally-closedcontact 13. The normallyelosed contact 13 of each switch 11 is connectedto the pole 12 of the next higher switch in the sequence, as shown bythe representative connection 16.

In the multi-conductor cable 20 are a plurality of individualconductors, each carrying a respective tone signal from atone signalgenerator or source, to successive normally-open contacts 14. Thenormally-open contact 14 of the first switch in the sequence receivesthe lowest pitched of the tone generator sources, in this case shown asC2, while the last or upper-key switch in the sequence 11 receivesthehighest tone, in this case C3. Thus, in the example shown. there are 13key switches in the sequence 11. spanning a complete octave in thechromatic scale.

The pole 12 of the first switch in the sequence is con? nected through aresistor 17 to an intermediate output p 3,422,454 Patented Jan. 14, 1969circuit, in this case a pedal divider 18. The pedal divider serves tocut the tone frequency inhalf, so that a tone one octave below thatapplied to its input appears at its output 19.

The circut thus far described constitutes the foundation to which thepresent invention is applied. lts operation is well known and issubstantially as follows:

The tone signal in the form of rectangular pulses of given frequencyresides on successive normally-open contacts 14, as represented bythewave form 21. Whenever a pedal key is actuated. the tone signal appliedto that particular key switch 11 goes through the pole l2, resistor 17,pedal divider 18, and to the output 19. Since higher pitch tones mustpass through the poles 12 of each switch of lower pitch, it follows thatthe actuation of any key switch of lower pitch will preempt the circuit.Thus, should several pedal keys be depressed simultaneously, only onetone signal, of the lowest pitch, will appear at the point 27 and beapplied to the pedal divider 18.

In accordance with the present invention, the normallyclosed contact 13of the last or highest switch in the sequence is employed as a take-offpoint for a percussion circuit 32. Also in accordance with the presentinvention,. the terminal 27 connected to the first pole 12 is groundedat 43 through a diode 28 poled as shown. These elements cause a negativegoing step voltage 29 to appear at 31, whenever a pole 12 is actuated.

Step 29 institutes charging of a capacitor 30, causing a negativesawtooth 33- to appear on the other side 56 of the capacitor 30. This isapplied through resistors 34 and 36 to one terminal 37 of a diode 38.The terminal 37 constitutes an input terminal for the percussion circuit32, to which the conductor 19 applies the output signal 39 of the pedaldivider l8. Normally, the'diode 38.is reversed biased, so that tonesignal 39 will not pass therethrough to the point 51- and thence to thepedal volume potentiometer 41. The appearance of the negative sawtooth33 on the terminal 37 allows the signal 39 to pass through the diode 38in decreasing amplitude as the saw;

tooth 33 rises. There is thus applied to the output 42 of the percussioncircuit 32 a percussed burst of pedaltone 39 having an envelope shape inaccordance with'tlt'e" ing sawtooth 33. .5:

Block 58 represents a final output systems of'any su b e form whichultimately-usually contains some 'torm electro acoustic transducerrepresented by the lou Q capacitor 30 are substantially at groundpotential, the.

capacitor is uncharged.

When any one of the switches 11 is operated sothat its pole 12 leavesits normally-closed contact 13, the

capacitor 30 begins to charge from the negative voltage source 26through the resistors 24, 46 34, 36, and circuit 18. Charging currentalso flows in resistor 47. The charging current produces the sawtooth33: as the charging current decreases. the potential 33 appearing zitthe terminal 37 rises to resume ground potential. The function ofcapacitor 40 is to round off the initial down step in the sawtooth 33,at the point 45.

Actuation of a switch 11, in addition to producing the step voltage 29at the terminal 31, also applies tone signal from the corresponding tonesignal source connected to the cable 20. through the resistor 17 andpedal divider 18, to the input terminal 37 of the percussion circuit 32.Since this signal is of positive polarity, as shown at 39, the diode 38constitutes a modulator or gate which blocks passage of tone signal 39unless the diode is forward biased a sufficient amount to let thesignals 39 pass. Such a bias is provided by the voltage 33, themagnitude of which is sufficient to unblock the gate formed by the diode38. This passes tone signal 39 through to the terminal 51, thencethrough the coupling capacitor 52, to the slider of the pedal volumepotentiometer 41. Resistors 53 and 54 and capacitors 50 and 50constitute voicing elements for the percussed .tones. Resistor 54' formsa return path for direct current flowing through diode 38.

As the terminal 56 of the capacitor 30 returns to ground potential, theamplitude of the tone signal 39 is steadily cut down by the loss offorward bias across the diode 38.

- Thus. the wave form 33 consititutes in effect a modulating signalwhich permits passage of a percussed burst of pedal tone 39 to theoutput circuit 58.

The connection between the point 27 and ground 43 has been shown as adiode 28 and this is the preferred circuit element. However, theessential characteristic of this element is that it be of low impedancerelative to that of the element (resistor) 24, with which it forms avoltage divider across the negative source of voltage 26 at leastinsofar as voltage poled as shown is concerned. If a resistance were tobe substituted at 28 having a value relatively low with respect to thevalue of resistor 24, the same phenomenon would be experienced but withless efficiency. y

In such a case there would be a small current constantly flowing throughthe element 28, switch sequence 11, and resistor 24, which would placethe point 27 at a potential somewhat below ground, the extent beingdetermined by the voltage division between 24 and 28. Upon actuation ofany of the switches 11, the terminal 31 would drop to a more negativepotential, as shown by the wave form 29. The principal difference inoperation would be the starting point for the step function 29; in thecase of the diode, it would start appreciably closer to ground than inthe case of a bilaterally-conducting element such as a resistor at 28.Employment of a diode as the element 28 permits virtually completefunctional isolation of the pedal divider input from the input of thepercussion circuit 32. The tone signals appearing in the switches 11have one polarity (positive) and goto the pedal divider, being isolatedfrom the percussion circuit 32 by the opening of a normallyclosedcontact 13. The signal 29 for driving the percussion ciicuit 32 is ofthe opposite polarity (negative) and is allowed to complete its circuitthrough the diode 28, without affecting the'tone signals. To thepositive going tone signal at the point 27, the diode is virtually anopen circuit and can be functionally ignored. To the negative goingpercussion signal 29, the diode is virtually a short circuit, thuspermitting virtually all of the voltage 29 to be developed at theterminal 31.

In the usual operation, the pedal switch 11 will be held down by theorganist for a time longer than the normal percussive time span of thewave form 33, so that the circuit will operate usually as describedabove. In case the organist wishes to inject a staccato effect evenshorter than the percussion time of circuit 32, he raises his foot fromthe pedal operating the switch 11 even before the percussive enveloperepresented by 33 has terminated. In this event tone signal at theoutput 42 terminates abruptly for either of two reasons.

In the first place, release of the switch 11 opens the contact 14,thereby isolating the pedal divider 18 from its source of tone signalsin cable 20. In the second place,

return of the pole 12 to the normally-closed contact 13 immediatelygrounds the control terminal 31 through the diode 28 to the ground point43. Since the point 31 had previously been negative, this reflects as apositive going step voltage at the point 31, which manifests itself inturn as a positive pulse at the point 56. This discharges the capacitor30 through the diode 57. The gate diode 38 immediately in effect becomesreversed biased and blocks any further passage of signals from point 37to point 51, even if such signals were still appearing on the input 19.

A second form of the invention, illustrated in FIGURE 2, has thecharacteristic that the tone signal is not so abruptly terminated asdescribed immediately above, even should the organist release the keyprior to culmination of the normal percussive envelope. The circuit ofFIG- URE 2 illustrates the adaptation of the present invention to a moresophisticated and refined keying circuit.

In the circuit of FIGURE 2, parts corresponding to those found in FIGURE1 have been designated with the same numeral followed by a suffix a. i

The normally-open contact 14a of each of the switches 11a in thesequence controls a respective tone signal from the cable 20a. Thecontrol connection is through a circuit which includes a back or reversebiased diode 65 and a resistor 66. The diode 65 constitutes a gate whichprevents tone signals 21 from passing to the output line 67 (through theindividual coupling capacitors 68), except when the diode 65 isforwardly biased by the actuation of a respective pole 12a. When this isdone, positive bias from a voltage source 69 is applied through aresistor 71 to the terminal 27a of the first pole 12a in the switchsequence 11a. The switches 11a are connected sequentially in the samemanner as in FIGURE 1, so that each switch 11a has constantly applied toits pole 12a the positive bias 69, unless one or more of the switcheslower on the keyboard has been moved to actuated position. Thus, onlythe lowermost pitch actuated at any one time will be sounded, the sameas in the FIGURE 1 circuit.

Application of the positive bias from 69 to the point 72 applies aforward bias to the diode 65, allowing the rectangular wave tone signal21 to appear at the point 72, and be applied through the capacitor 68and line 67 to the input of the pedal divider 180. As in the circuit ofFIGURE 1. this signal is divided in frequency and appears as shown at39a at the point 190, where it en- I counters the back biased diode 38a.

A percussed burst of signal is allowed to pass through the diode 38:: bythe application thereto of a sawtooth gating pulse 331:. Thissubstantially is the same as the pulse 33 of FIGURE l, except it ispositive instead of negative, and, hence, is applied to the oppositepole of the diode 38. U

The sawtooth 33a is the result of a positive going step voltage 29aapplied to the point 31a by the actuation of any one of the poles 12a.Upon operation of any switch 11a, a charging current fiows from thesource 69, through the pole 12a, isolating diode 73, and thence to theterminal 31a, capacitor 30a, diode 77, resistor 78, diode 38a andcircuit 18a. Charging current also flows throughrcsistor 74 to groundconnection 76. Since the resistance 74 is much larger than theresistance 71, substantially the full voltage from the source 69 ispromptly felt on the terminal 31a. As the capacitor 30a charges up, thevoltage at 56a gradually drops back to ground potential, as shown at330.

The sawtooth voltage 330 passes without substantial attenuation throughthe diode 77 and resistor 78 to the point 79, where'it serves toforwardly bias the diode 38a and allow thesignal 39a to reach the point79. From there the tone signal 39a passes through the coupling capacitor81 to the output terminal 42a. Resistors 82 and 83 and capacitorconstitute a voicing network for the percussed tone signals.

The function thus far described for FIGURE 2 is substantially the sameas the function of the corresponding parts in FIGURE 1. The chiefdifference in function between the circuits of FIGURE 2 and FIGURE 1occurs in case the organist releases the actuated pole 12a before thepercussion pulse or envelope 33a has run its full course. In such anevent, the FIGURE 2 circuit produces a slight tone sustain, which tomost ears is more pleasing than the abrupt termination produced byFIGURE 1.

The circuit of FIGURE 2 is employed in an organ having an appreciablesustain to the tone after the release of a key. The organ also has afeature which prematurely terminates the sustain should a second key beplayed before the sustained tone has run its course. Such features aredisclosed in co-pending application, Ser. No. 378,117, filed June 26,1964, now abandoned and the continuation-in-part thereof Ser. No.701,032, filed J an. 4, 1968.

The persistance of the tone signal 39a at the point 19a, after departureof a pole 12a from contact 14a, is due to the pedal sustain featureembodied in FIGURE 2. This is effected by storage of gate openingpotential on respective capacitors 86, which contain a residual chargethat maintains the operated gate 65 open long enough to sustain thetones at 19a for a predetermined period.

Since the tone is available at 19a, it is desirable to cause it to taperoff somewhat less abruptly than would be the case if the gate 38a wereto be closed abruptly by removal of the forward bias from point 79. Thisis effectuated by the storage of a charge on the relativelysmallcapacitor 87. The abrupt termination of the positive sawtooth 33aappearing at the point 56a is not reflected on to the capacitor 87because of the presence of the isolating diode 77. Thus, the terminationof the sawtooth 33a simply causes the diode 77 to appear substantiallyas an open circuit to the capacitor 87, which then proceeds to dischargethrough the resistor 78, diode 38a, and the circuitry of the pedaldivider 1802. This discharge is relatively rapid and produces a veryshort tail. It is, however, less abrupt than the cutting off which wouldotherwise occur, and produces for many purposes a more desirable tonaleffect.

Closing of switch 94 grounds point 79 and disables the percussioncircuit completely.

As alluded to hereinbefore, the circuit of FIGURE 2 involves certainpedal sustain and pedal cancel circuitry illustrated schematically inpart by the block 89. Such circuitry also feeds to the ultimate outputcircuit represented schematically at 91, which includes some form ofelectro acoustic transducer such as loudspeaker 92.

It is to be understood that in both FIGURE 1 and FIGURE 2 the tonesignal sources which feed the cable 20 are ultimately returned, at leastinsofar as tone signal frequencies are concerned, to the same ground asillustrated in these figures; and that the his voltages referred toherein have reference to that same ground potential.

It will be readily seen also that the pedal divider is not necessary tothe functioning of the present invention. If desired, the inventionherein could be employed without the pedal divider simply by passing thesame frequency from the cable 20 directly to the diode 38 withoutdividing the frequency.

While the instant invention has been shown and described herein in whatis conceived to be the most practical and preferred embodiments, it isrecognized that departures may be made therefrom within the scope of theinvention which is, therefore, not to be limited to the detailsdisclosed herein but is to be afforded the full scope of the inventionas hereinafter claimed.

What is claimed is:

1. A keying circuit for a monophonic electronic musical instrument,comprising:

a sequence of double-throw switches, each having a pole, anormally-closed contact, and a normallyopen contact; a plurality ofplaying keys, one for each said switch, and linked to a respective polethereof, each said pole residing on the normallyclosed contact, exceptwhen the corresponding key is in actuated position;

a plurality of different tone signal sources;

an intermediate output system;

a plurality of first-circuit means each connected between anormally-open contact of a switch and a respective tone signal sourceand effective to apply a tone signal to said intermediate output systemwhenever the corresponding key is actuated so as to move the pole fromthe normally-closed to the normally-open contact;

the normally-closed contact of each switch being sequentially connectedto the next succeeding switch in the sequence, except for the lastswitch in the sequence;

second circuit means connected to the pole of the first switch in saidsequence for electrically returning said last-named pole to saidplurality of tone signal sources;

step-function circuit means for generating a step-function signal inresponse to actuation of any of said switches from its normally-closedto its normallyopen contact;

a final output system;

percussive envelope means for applying tone signals from saidintermediate output system to said final output system;

said step-function circuit means being connected to said percussiveenvelope means for causing said percussive envelope means to pass apercussed burst of tone signal from said intermediate output system tosaid final output system in response to each application of astep-function signal.

2. In a keying circuit for a monophonic electronic musical instrumenthaving a sequence of double-throw switches, each having a pole, anormally-closed contact and a normally-open contact; a plurality of keyscorresponding to said switches and connected respectively thereto, eachkey when actuated serving to move the pole of the corresponding switchfrom the normally-closed to the normally-open contact; a plurality ofdifferent tone signal sources corresponding to said switches, eachhaving its output connected to the normally-open contact of thecorresponding switch; the normally-closed contact of each switch exceptthe last in the sequence being sequentially connected to the pole of thenext succeeding switch in the sequence; an intermediate output systemconnected to the pole of the first switch in the sequence, whereby uponactuation of any key, the tone signal from its corresponding tone signalsource is applied to said intermediate output system, the improvementcomprising:

a percussion circuit including:

an input connected to the output of said intermediate output system, anoutput adapted to be connected to a final output system, and a controlterminal connected to the normallyclosed contact of the last switch insaid sequence;

a source of bias potential connected between said control terminal andsaid pole of said first switch in the sequence;

diode means connected in series with and between said source ofpotential and said pole of said I first switch;

gating means for passing tone signals from the input to the output ofsaid percussion circuit in response to existence of an input pulse onsaid gating means;

pulse-shaping means responsive to voltage change appearing on saidcontrol terminal for applying a percussion envelope pulse to said gatingmeans, thereby to pass a burst of percussed tone signal from the inputto the output of said percussion circuit.

3. In a keying circuit for a monophonic electronic musical instrumenthaving a sequence of double-throw switchces, each having a pole, anormally-closed contact and a normally-open contact; a plurality of keyscorresponding to said switches and connected respectively thereto, eachkey when actuated serving to move the pole of the corresponding switchfrom the normallyclosed to the normally-open contact; a plurality ofdiferent tone signal sources corresponding to said switches, each havingits output connected to the normally-open contact of the correspondingswitch; the normally-closed contact of each switch except the last inthe sequence being sequentially connected to the pole of the nextsucceeding switch in the sequence; an intermediate output systemconnected to the pole of the first switch in the sequence, whereby uponactuation of any key, tone signal from its corresponding tone signalsource is applied to said intermediate output system, the improvementcomprising:

a percussion circuit including:

an input connected to the output of said intermediate output system, anoutput adapted to be connected to a final output system, and a controlterminal connected to the normally-closed contact of the last switch insaid sequence;

a source of bias potential connected between said control terminal andsaid pole of said first switch in the sequence;

first impedance means connected in series with and between said sourceof potential and said control terminal;

second impedance means connected in series with and between said pole ofsaid first switch and the other side of said source of potential, saidsecond impedance means appearing at least to a voltage of given polarityas a low impedance rela tive to said first impedance means;

gating means for passing tone signals from the input to the output ofsaid percussion circuit in response to existence of an input pulse onsaid gating means;

pulse-shaping means responsive to voltage change appearing on saidcontrol terminal for applying a percussion envelope pulse to said gatingmeans, thereby to pass a burst of percussed tone signal from the inputto the output of said percussion circuit.

4. A keying circuit for a monophonic electronic musical instrument,comprising:

a sequence of double-throw switches, each having a pole, anormally-closed contact, and a normallyopen contact; a plurality ofplaying keys, one for each said switch, and linked to a respective polethereof, each said pole residing on the normallyclosed contact, exceptwhen the corresponding key is in actuated position;

a plurality of different tone signal sources;

an intermediate output system;

a plurality of first-circuit means each connected between anormally-open circuit of a switch and a respective tone signal sourceand effective to apply a tone signal to said intermediate output systemwhenever the corresponding key is actuated so as to move the pole fromthe normally-closed to the normally-open contact;

the normally-closed contact of each switch being sequentially connectedto the next succeeding switch in the sequence, except for the lastswitch in the sequence;

triggering circuit means for generating a triggering signal in responseto actuation of any of said switches from its normally-closed to itsnormally-open contact;

a final output system;

modulator means for applying tone signals from said intermediate outputsystem to said final output system;

said triggering circuit means being connected to said modulator meansfor causing said modulator means to pass a percussed burst of tonesignal from said intermediate output system to said final output systemin response to each application of a triggering signal.

No references cited.

ARTHUR GAUSS, Primary Examiner.

ROBERT H. PLOTKIN, Assistant Examiner.

US. Cl. X.R.

